1. Field of the Invention
The present invention relates to a method and apparatus for sound pickup using a plurality of microphones, and to a method and apparatus for sound reproduction using loudspeakers or headphones based on a sound signal picked up by the sound pickup method and apparatus.
2. Description of the Related Art
Binaural recording is one sound pickup method for recording sound from sound sources placed in an acoustic space while maintaining information about the direction of incoming sound.
Another sound pickup method other than binaural recording for recording sound from sound sources while maintaining information about the direction of incoming sound is to use multiple directional microphones as pickup microphones.
In the multi-directional microphone method, a plurality of, e.g., three, directional microphones are placed with their directional ranges covering different areas for individually picking up sound from different areas. In the sound reproduction side, a plurality of, e.g., three, loudspeakers are placed similarly to the pickup areas for reproducing and outputting sound to a listener.
If the microphones have insufficient directional selectivity, a matrix operation is performed on sound signals output from the microphones to obtain sharper directivity, resulting in high spatial resolution during sound reproduction. A directional characteristic is produced by a matrix operation, and therefore an omni-directional microphone may be used as a pickup microphone.
Such a multi-directional microphone method (including the use of omni-directional microphones, in which a directional characteristic is produced by a matrix operation) is advantageous over the binaural method to give a natural auditory sensation to a listener who changes his/her head orientation during sound reproduction as if he/she changes his/her head orientation in the recording site.
Japanese Unexamined Patent Application Publication No. 2002-271885 discloses a microphone system having three pairs of microphones placed around a reference microphone, in which sound signals output from the microphones are subjected to digital signal processing to control the directional characteristics of the microphones.
Japanese Unexamined Patent Application Publication No. 9-70094 discloses a headphone apparatus that detects motion of the head of a listener who wears a headphone and that processes multi-channel sound signals depending upon the orientation of the listener's head to localize the sound image outside the listener's head in front of or behind the listener.